When a tenant has a written rental agreement that begins and ends on specific dates, the rent is generally fixed at the price listed in the rental agreement until the time of renewal. A landlord can reserve the right to increase the rent during the tenancy, but would need to provide in the lease the specific terms and notice required to increase rent. If no such clause exists in the lease, the landlord will have to wait until the lease expires before he/she can change the terms of the rental agreement.
If the landlord attempts to increase your rent in violation of your lease, make clear to the landlord, in writing, that his/her actions are not allowed under the lease.
How to use a form letter.